Rotating shroud



Sept. 13, 1960 E. P. WARNKEN ROTATING" SHROUD 5 Shets-Sheet 2 Filed May28, 1957 IN VEN TOR. ELMER I? WARN KEN BY Sept. 13, 1960 filed May 28,1957 E. P. WARN KEN ROTATING SHROUD 3 Sheets-Sheet 3 INVENTOR.

ELMER P. WARN/(EN d g Azz fys.

United States Patent ROTATING SHROUD Elmer P. Warnken, Cincinnati, Ohio,assignor, by mesne assignments, to Studebaker-Packard Corporation, SouthBend, Ind., a corporation of Michigan Filed May 28, 1957, 581'. No.662,229 1 Claim. (11. 253-77 This invention relates to shrouds forsecuring and rigidifying the outer ends of a row of blades in a rotorfor an aircraft engine, or the like.

Rotor blades have a tendency to gain or lose tip angle when ofsubstantial size, especially length, and when rotating at high speeds;therefore, it is an object of this invention to provide a shroud thatwill so secure and rigidity the tips of the blades that the proper tipangle is maintained in operation.

A further object of this invention is to provide a shroud which controlsthe tip amplitude during flight conditions to reduce the tendency towardblade deflection and to minimize vibration of the rotor blades.

A further object of this invention is to provide a rotor shroud whichties together the blades in a row to allow every blade in the row toaccept its share of mechanical loads which develop during rotating stallof the blades, i.e., when only a portion of the blades are inaero-dynamic stall. I A further object of this invention is to provide arotor shroud whichmaintains a minimum tip clearance between rotatingportions of the compressor and the casing thereof, and thereby minimizesrecirculation of air around the tips of the blades.

\A further object of this invention is to provide a light- .Weightsegmental shroud that can be readily assembled with rotor blades.

A further object of this invention is to provide a shroud which ismounted .on but not attached to the rotor blades and in which bushingsin the shroud are provided with radial slots into which tips of therotor blades fit so that the shroud can expand or contract with respectto the blades without causing buckling of the blades or shroud.

A further object of this invention is to provide a shroud which is heldtogether by a continuous winding which accepts the load imposed by rapidrotation.

A further object of this invention is to provide a segmental shroudhaving outwardly projecting channel-shaped segments mounted on the tipsof the blades, the segments forming an air-seal with the casing of therotor, the segments being held together by a resin-impregnated windingof substantially continuous glass fibre rovings, or the like, woundbetween the flanges of the channel-shaped segments and bound by theresin.

The above and other objects and features of the invention will in partbe apparent and will in part be obvious to those of ordinary skill inthe art to which this invention pertains from the following detaileddescription, and the drawings, in which:

Figure 1 is a fragmentary view in transverse section of a portion of theair compressor section of a jet aircraft engine provided with rotorblade shrouds constructed in accordance with an embodiment of thisinvention;

Fig. 2 is a fragmentary view of a portion of the rotor blades and rotorshroud of one row of rotor blades;

Fig. 3 is a view in section taken on a line III-III in Fig. 2;

2,952,442 Patented Sept. 13, 1960 Fig. 4 is a fragmentary exploded viewof the rotor shroud and one blade of the rotor;

Fig. 5 is a view in side elevation of a blade tip bushs;

Fig. 6 is a view in elevation showing the interior of a fragmentaryportion of a shroud of a rotor constructed in accordance with anotherembodiment of this invention;

Fig. 7 is a view in section of the shroud illustrated in Fig. 6 and of aportion of a device for making the shroud, the section being taken onthe line VII-VII in Fig. 6; and

Fig. 8 is a view in section of the shroud taken along the line VIII-VIIIin Fig. 6, a portion of one blade being shown in association therewith.

In Figure l a portion of the compressor section 10 of a jet aircraftengine is illustrated. The compressor section includes an outer casing12 in which stator blades 13 are mounted. Within the casing is a rotor14 provided with rows of rotor blades 16.

As indicated in Fig. 2, a plurality of blades 16 comprises a row. Theouter ends of the blades 16 of each row are secured to a rotating shroud17. As shown in Fig. 4, the shroud 17 includes a plurality ofblade-receiving channel-shaped segments 18 forming a ring or shell and aplurality of hoop-receiving channel-shaped segments 19 forming a secondring or shell. The segments 18 and 19 are formed of resin-impregnatedfibre glass cloth molded to channel shape, as shown. The angle subtendedby each segment may be of any desired size,

but preferably is degrees or less, but may be any size up to 360degrees. Preferably, the blade receiving segments 18 are short segments,each of which receives the end of one blade, and the hoop-receivingsegments 19 are approximately 60 degree segments. The segments 19 areslightly narrower than the segments 18, as indicated in Fig. 3 and arereceived between flanges 21 and 22 of the blade-receiving segments.

The rows of segments are separated by a cellular member or honeycomb 23of perforated, light-Weight, rigid material, such as resin-impregnatedfibre glass or perforated aluminum of light weight but sufficientlyrigid to maintain the segment rings separated when the rotor rotates athigh speed. Preferably, the honeycomb is formed of aluminum which hascut away portions or perforations to give it light weight, of the orderof approximately eight pounds per cubic foot.

The segments of the blade-receiving ring are provided with slots 26 inwhich bushings 27 are received. Each of the bushings 27, as shown inFig. 3, is provided with a relatively deep slot 28 in which the tip ofone of the blades 16 is received. In addition, each bushing is providedwith an annular slot or groove 29 in which the edges of the segment arereceived. As shown, the outer face 31 of the bushing conforms in shapeto and engages the outer segment 19. The bushings may be formed of ahard, stiff, durable plastic material, such as nylon or Teflon. Thehoneycomb is also provided. with a slot 32 of sufiicient size to receivethe bushing. The honeycomb thereby aids in holding the bushing in place.

The blade-receiving slot of each bushing extends substantially radiallyof the shroud segments, and the tips of the blades are slidably receivedin the slots of the bushings.

The segments are cemented together and to the honeycomb material. Asshown in Fig. 3, the edges 33 and 34 of the flanges of the segment rings18 and 19 are substantially aligned. As shown in Fig. 1, the shroud isreceived in a slot 35 in the inner face of the casing, and the edges ofthe flanges of the segment rings are very closely spaced from the baseof the slot 35 to form an air-seal between the rotating elements and thecasing.

The contour of the inner races of the segments 18 is shown as asubstantially smooth curve, but the contour may be varied, particularlyat the area adjacent the slots 26 as required to give a properaerodynamic shape.

The segments of the shroud are reinforced and held together by aretaining winding 36 of elongated fibres of resin impregnated glass, orthe like. Winding 36 comprises many turns on the segments in the spacebetween the flanges of the channels. Preferably, as shown in Fig. 3, thethickness of the winding is less than the depth of the flanges 37 of thehoop-receiving segments so that a short air gap G between the winding 36and the casing 12 will be formed, as shown in Fig. l. The winding may bemade with fibre glass rovings impregnated with a suitable resin such asan epoxy resin or a phenolformaldehyde resin. The rovings are woundnumerous times around the segment rings to provide a substantiallycontinuous winding or hoop of great strength which holds the segmentsfirmly in assembled relation.

If desired, all portions of the shroud may be formed of metal, and'thewinding may be formed of stainless steel wire, or the like. When steelwire is used for the winding, adjacent convolutions may be lockedtogether by an appropriate solder, such as silver solder, or the like.The solder may be applied to the Wire before it is wound, and, then,after the rotor has been wound, the rotor may be heated to cause fusionof the solder to tightly grip the wire and hold it in place.

When the rotor is in operation, the shroud may ex- \pand slightlybecause of centrifugal force, and, as it expands, the bushings can slideoutwardly of the blade tips without causing distortion of the blades orof the shroud.

In Figs. 6-8 inclusive is shown a shroud 41 constructed in accordancewith another embodiment of this invention. The shroud 41 includes acentral strip or annular shell 42 which may be formed of strong,durable, resilient material such as one of the plastic materials, suchas nylon and Teflon. Surrounding the strip 42 is a-ring or retainingband 43 made up of a filamentary winding which may be formed ofelongated, resin-impregnated, glass fibres or other suitable filamentarymaterial. The Winding ring 43 is formed on a mandrel 44 (Fig. 7) whichmay be generally cylindrical and has an annular shoulder 46. A ring 47slides on one end of the mandrel and co-operates with the shoulder 46 toform an annular slot in which the winding is formed.

The central strip 42 may be formed flat. Aplurality of equally spacedsockets 48 are formed in the central strip. The central strip is woundaround the mandrel 44, the central strip being just long enough to forma complete ring. Then the resin-impregnated filamentary material iswound in the slot surrounding the strip 42. The assembly may be heatedto set the resin to hold the filamentary material in place. Then thering 47 and the assembly are slid off the mandrel 44 and the resin maybe cured in the usual manner to form the completed shroud 41. The shroud41 is mounted on blades 49, only one of which is shown, in the mannerindicated in Fig. *8. Each blade 49 is provided with a tang .51 at-theouter end thereof. The tang '51 fits in and is .slidably received in oneof the sockets 48.

The shroud illustrated in Figs. 6-8 inclusive operates in the samemanner as described earlier. As shown, the edges of sockets extendsubstantially radially, so that, as the shroud expands slightly duringoperation, the shroud can move out or in along tangs 51, while theshroud holdsthe blades in proper position.

It will be apparent to those skilled in the art to which this inventionpertains, that the illustrated embodiments may be modified or changedwithout departing from the spirit and scope of the appended claims.

Therefore, what I claim as new and desire'to secure by Letters Patentis: l

A rotor which comp-rises a plurality of radially extending rotor blades,an annular shell surrounding the rotor blades, there being a pluralityof sockets in said annular shell extending radially of and looselyreceiving in radially overlapping relation the tips of the rotor blades,the tips of the rotor blades being slidable lengthwise of the sockets,whereby the annular shell may expand and contract independently of therotor blades, the sockets terminating short of the outer face of saidannular shell, whereby relative sliding movement of the shell and therotor blades is limited, and a substantiallycontinuous winding offilamentary material outboard of and overlying the sockets and embracingtheannular shell to form a retaining band surrounding the annular shell.

References (Zited in the file of this patent UNITED STATES PATENTS764,450 Geisenhoner July 5, 19.04 1,547,836 Steenstrup July 28, 19252,681,788 Wosika June 22, 1954 FOREIGN PATENTS 13,881 Great Britain 1905228,250 Germany Nov. 5, 1910 267,405 Great Britain Mar. 17, 1927

